Martin SP Lifespan acoustic guitar strings are used by Martin on the majority of its production guitars. Martin SP Lifespan with Cleartone proprietary technology provides a rich full tone with the added benefit of longer life. The Martin SP Lifespan acoustic guitar strings start with ultra-pure steel SP core wire, which delivers a perfect combination of tensile strength and response. Bronze electroplating is added to protect and enhance the core wire, which is complemented by the wraps that bring the full, rich tone players demand. Finally, Martin's custom wrapping technique ensures tight tolerances to gauge and tension. Martin SP sets are sent to Everly Music for treatment with Cleartone proprietary technology. This treatment provides the thinnest protection in the industry and does not flake or peel. The treatment protects both the wrap and core wire by repelling dirt and grime that can deaden a string. Wrap windings remain open and uncovered to permit natural vibration patterns. The Cleartone proprietary technology preserves and protects the natural rich full tone of the Martin SP strings.